The invention concerns a gearset-drive unit with speed detection, in particular for use in a motor vehicle, according to the general class of the independent claims.
A motor gearset-drive unit for adjusting equipment parts of motor vehicles with a commutator motor was made known in EP 0 865 148 A1. According to said publication, a substantially pot-shaped motor housing contains a motor armature with an armature shaft extending out of the motor housing. The armature shaft is supported between the motor housing and the gearset housing by means of a spherical cap bearing. A collector and a ring magnet are located on the armature shaft between the motor armature and the spherical cap bearing. The outer circumference of the ring magnet is magnetized in alternating north and south poles. The changing magnetic field is detected by two Hall-element sensors offset from each other by 90°, and it is evaluated by control electronics located on an electronic printed-circuit board. The electronic printed-circuit board extends into the motor housing into the immediate vicinity of the ring magnet. This arrangement of the electronic printed-circuit board within the motor housing or in the region of the brush holder is very complicated and inflexible. In addition, the brush sparking interferes with the speed sensors.